Bug 235940
| Summary: | [JAVA_BLOCKER] timekeeping starvation (sched_football hangs on RHEL5 RT) | ||||||||
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| Product: | Red Hat Enterprise MRG | Reporter: | IBM Bug Proxy <bugproxy> | ||||||
| Component: | realtime-kernel | Assignee: | Clark Williams <williams> | ||||||
| Status: | CLOSED CURRENTRELEASE | QA Contact: | |||||||
| Severity: | medium | Docs Contact: | |||||||
| Priority: | medium | ||||||||
| Version: | 1.0 | ||||||||
| Target Milestone: | --- | ||||||||
| Target Release: | --- | ||||||||
| Hardware: | x86_64 | ||||||||
| OS: | Linux | ||||||||
| Whiteboard: | |||||||||
| Fixed In Version: | 2.6.21-2.el5rt | Doc Type: | Bug Fix | ||||||
| Doc Text: | Story Points: | --- | |||||||
| Clone Of: | Environment: | ||||||||
| Last Closed: | 2007-05-15 02:19:47 UTC | Type: | --- | ||||||
| Regression: | --- | Mount Type: | --- | ||||||
| Documentation: | --- | CRM: | |||||||
| Verified Versions: | Category: | --- | |||||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||||
| Embargoed: | |||||||||
| Attachments: |
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Description
IBM Bug Proxy
2007-04-10 21:45:36 UTC
Created attachment 152183 [details]
tested cycles-accumulated patch sent to Ingo
----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-04-10 19:32 EDT ------- Any objections to the patch from RedHat's side? Assigning to Clark to consider backporting Ingo's patch from 21 to 20. Just a small update, Keith Mannthey has seemingly triggered this issue w/ 2.6.21-rt (which includes my fix). So we're digging to figure out if additional changes may be needed. ----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-04-24 18:01 EDT ------- I'm confirmed an issue still exists with regards to timekeeping starvation in 2.6.21-rc6-rt0. I'm still working to narrow it down. ----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-04-24 21:22 EDT ------- Ok! I found it! Ingo has added a vsyscall hack (.sysctl_enabled = 2) on x86_64, where the vsyscall just quickly returns the last calculated value of xtime instead of reading the clocksource hardware (to improve speed). This means gettimeofday has tick resolution, and further it loses robustness under heavy -RT load (allows for starvation, as xtime won't be incremented until the timer_softirq runs). I'm testing a patch to set the .sysctl_enabled back to 1 as the safe default. Created attachment 153395 [details]
sysctrl-fix.patch
----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-04-24 21:36 EDT ------- don't enable the vsyscall_gtod returns walltime hack by default Simply sets the vsyscall .sysctrl_enable to 1 instead of 2 to avoid the vsyscall returns xtime hack that is prone to starvation. ----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-04-24 21:42 EDT ------- Patch sent to Ingo. ----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-05-02 20:02 EDT ------- I've confirmed Ingo included the patch in 2.6.21-rt1. This can be closed once RH rebases on 2.6.21. ----- Additional Comments From jstultz.com (prefers email at johnstul.com) 2007-05-10 18:23 EDT ------- Verified fixed in 2.6.21-2.el5rt kernel from Clark's repo. |